Ultrasonically sealed side seam on cup

ABSTRACT

A container comprising a tubular body part having a longitudinal lapped side seam and a bottom part attached to one end thereof, characterized in that the overlapping portions of the side seam are adhered by ultrasonic bonding to provide a bonded area longitudinally of the side seam of predetermined transverse width throughout the major portion of its length and a bonded area at the top of greater transverse width which is at least several millimeters in length longitudinally of the seam.

This is a continuation of co-pending application Ser. No. 765,171 filedon Aug. 12, 1985, now abandoned, which is a continuation of 06/534,259filed 9/20/83, now abandoned, which is a continuation of 06/340,357filed 1/18/82, now abandoned, which is a division of 06/217,217 filed12/17/80, now U.S. Pat. No. 4,374,697.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a container consisting of a body and abottom plate of cardboard laminated with a plastic material, and amethod and a device for manufacturing the same.

More particularly, the present invention relates to a container in whichthe side superimposed portion of the container is completely adhered toa distance of 2 to 3 mm from the upper end, and the upwardly foldedportion of the lower end of the body is adhered to the downwardly foldedportion of the periphery of the bottom plate; and to a method and adevice for manufacturing the body and the bottom plate of such acontainer.

2. Description of the Prior Art

Plastic laminated paper sheets have conventionally been used forcontainers for holding liquids. In many such containers, juices, ricewine or the like are exposed to portions laminated with paper sheets,aluminum foils, synthetic resin, or the like for facilitatingflowability of the content of the container at room temperature, and thecontainers are sealed with film-shaped lids. In general, the liquid mustbe heated to a high temperature for heat-sealing the container. In sucha case, when 2 to 3 mm of the side superimposed portion from the upperend of the cup is not completely adhered, the contents seep from theupper end of the cup to the outside under capillary action. This hindersthe heat-sealing of the lid and results in incomplete sealing. Thispermits leakage of the contents to the outside, introduction of air, andso on. Thus, this container is unsuitable as a container for holdingliquids which are flowable at room temperature. The superimposed portionof a blank is generally sealed linearly in a certain width. However, asshown in FIG. 2, when viewed from its section, a sealed portion a doesnot extend to the inner end surface. In this figure, numeral 1 denotes acup body and 2 is a superimposed portion at both ends of the blank ofthe body. In some cases, the side end of the blank which comes insidethe container is skived to a certain extent from the outside. Theunskived portion is folded outwardly, and the side ends of the body aresuperimposed on each other and sealed so that only the portion of thebody which is laminated with polyethylene is brought into contact withthe liquid inside the container. Thus, the permeation of the liquid whenthe side edge is cut and exposed to the liquid is eliminated. In anycase, in a conventional cup-shaped sealed container for holding liquids,the sealed portion is as shown in FIG. 2. Since the liquid inside thecontainer is at a high temperature when the lid is heat-sealed, theliquid permeates by capillary action to the outside from an unsealedportion b. This hinders the heat-sealing and has presented problems inthe manufacturing procedure.

Conventionally, when adhering the side superimposed portion of thecontainer body for forming the body, the contacting surface of anultrasonic horn to the upper side superimposed portion is flat. However,when the side superimposed portion is adhered with such a conventionalultrasonic horn, the adhesion gradually weakens from the center of thehorn contacting surface toward the outside, and the adhesion of bothends, especially the portions 2 to 3 mm from the ends, is not complete.When an attempt is made to completely adhere these portions, problemsarise such as cracks at the central portion of the side superimposedportion.

A device has conventionally been used for hot-pressing the bottom plateof the container. The device consists of an outer press mold forreceiving the adhering portion of the lower end of the container bodyand the periphery of the bottom plate, and further consists of aknurling tool rotating inside the outer press mold. Since there are anumber of recesses and projections at the portion of the knurling toolwhich is brought into contact with the above-mentioned adhering portionin the direction of rotation of the knurling tool, cracks form there,leading to leakage of the contents and so on.

SUMMARY OF THE INVENTION

It is, therefore, the primary object of the present invention toprovide, in a container consisting of a container body and a bottomplate of cardboard laminated with a plastic material as raw materials, acontainer in which the side superimposed part of the body is completelyadhered and the upwardly folded part of the lower end of the body andthe downwardly folded part of the periphery of the bottom plate arecompletely adhered for excellent sealing effects; and to provide amethod and a device for manufacturing the same.

In order to accomplish the above and other ends, the present inventionprovides a container characterized in that the side superimposed portionof the body is completely adhered to a distance of 2 to 3 mm from theupper end, and the upwardly folded portion of the lower end of the bodyand the downwardly folded portion of the periphery of the bottom plateare adhered.

According to another object of the present invention, there is provideda forming device for manufacturing such a container comprising anultrasonic welding device mounting an ultrasonic horn having a stepbetween a contacting surface to the side superimposed portion of thecontainer 2 to 3 mm from the upper end and a contacting surface to theportion below the portion 2 to 3 mm from the upper end; an outer pressmold in which can be fitted the outer circumference of the adheringportion of the periphery of the bottom plate and the body, said outerpress mold having a circular hole at the center for a knurling shaftwith a diameter sufficiently larger than that of the shaft; and aknurling tool having a disk-shaped body for outwardly pressing saidadhering portion against the inner wall of the outer press mold, havingan outer circumferential wall that is in contact with the adheringportion of the lower end of the container body and the bottom plate, andhaving an annular groove of certain width at its central portion, saidknurling tool revolving on its axis as well as along the inner wall ofthe circular hole.

According to another aspect of the present invention, there is alsoprovided a method for manufacturing a container of the type described,said container consisting of the body and the bottom plate manufacturedwith such a forming device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a conventional sealed container;

FIG. 2 is an enlarged section taken on the line 2--2 of FIG. 1 and onthe line 2--2 of FIG. 3;

FIG. 3 is a vertical diametral section of the sealed container of thepresent invention;

FIG. 4 is an enlarged section taken on the line 4--4 of FIG. 3;

FIG. 5 is a perspective view illustrating the first embodiment of thehorn of an ultrasonic welding device of the present invention;

FIG. 6 is a perspective view illustrating the horn contacting portion ofthe device shown in FIG. 5; and

FIG. 7 is a partial sectional view illustrating the manner in which thewelding is performed by the ultrasonic welding device of the presentinvention.

FIG. 8 is a perspective view illustrating the shape of the hornaccording to the second embodiment used in the ultrasonic welding devicefor the container of the present invention;

FIG. 9 is a front view of the horn shown in FIG. 8;

FIG. 10 is a perspective view illustrating the shape of the contactingportion of the horn shown in FIG. 8;

FIG. 11 is an explanatory view illustrating the manner the welding isperformed by the welding device adopting the horn shown in FIG. 8;

FIG. 12 is a perspective view of a knurling tool used for forming thebottom part of a conventional container;

FIG. 13 is an explanatory view of the bottom forming device of thecontainer of the present invention; and

FIG. 14 is a perspective view of the knurling tool of the bottom formingdevice of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is, therefore, the primary object of the present invention toprovide, in a container consisting of a container body and a bottomplate of cardboard laminated with a plastic material as raw materials, acontainer in which the side superimposed part of the body is completelyadhered and the upwardly folded part of the lower end of the body andthe downwardly folded part of the periphery of the bottom plate arecompletely adhered for excellent sealing effects; and to provide amethod and a device for manufacturing the same. The present inventionwill now be described in more detail with reference to the accompanyingdrawings. FIG. 3 is an explanatory view of a container of the presentinvention in which the side seal 2 to 3 mm from the upper end, asdesignated by numeral 3, is formed into a completely sealed portion withan adhesive to eliminate the problems of the prior art. The sectionalong the line A--A of FIG. 3 is shown in FIG. 4. As may be seen in FIG.2 from the sectional view along the line B--B of FIG. 3, at tne portionof the side seal below the portion 2 to 3 mm from the upper end, thesealing is incomplete, leaving a non-sealed portion b. At the portionbelow the portion 2 to 3 mm from the upper end, this presents fewerproblems for heat-sealing the lid, so that this condition is acceptable.However, by performing complete sealing of the sealed portion 3(completely sealed portion) 2 to 3 mm from the upper end, the heatsealing with a closed lid at a high temperature may be completelyperformed.

Describing the method and the device for welding the body superimposedportion of the container of the present invention, FIGS. 5 and 6 showthe first embodiment of the horn of the ultrasonic welding deviceaccording to the present invention, in which a slightly steppedlongitudinal groove is formed at the center of the contacting surface ofthe horn, and both sides of the groove of the contacting surface aregradually stepped toward the center to provide an excellent result. Inthese figures, numeral 4 denotes first stepped portions, 5 is a secondstepped portion and 6 is a central longitudinal groove, and 7 arecontacting surfaces. The dimensions of the horn were as follows: thestepped difference between the contacting surfaces 7 and the secondstepped portion was 0.02 mm, the width of the lower surface of the hornwas 12.7 mm, the sides of the contacting surfaces were each 4.5 mm, thelength of the contacting surfaces was 152.4 mm, the length of the firststepped portions 4 were each 11.2 mm, the length of the second steppedportion were each 90 mm, the depth of the central longitudinal groove 6was 0.02 mm, and the width of the central longitudinal groove 6 was 3.7mm. With an ultrasonic welding device with such a horn, the ultrasonicwelding of the body superimposed portion of the blank was performed at20 HK and 3 KW by the blank setting method, the diameter of the aircylinder being 3 inches.

    ______________________________________                                        Contact time                                                                           Holding time  Air pressure                                                                             Loading                                     (seconds)                                                                              (seconds)     (psi)      (%)                                         ______________________________________                                        0.3      0.1-0.3       70         50-60                                       0.35     0.1-0.3       60         50-60                                       0.4      0.1-0.3       50-70      50-60                                       ______________________________________                                    

With this method, it was possible to seal the entire surface withoutcracks. FIG. 7 shows a partial section of the side seal welded byultrasonic welding. In this figure, symbols A and B denote edges at theends of the blank, C is a skived portion, and D is a receiving jig.

Complete sealing was possible, and no cracks were observed in eitherpre- or post-oscillation (oscillation was performed after setting thehorn).

The use of such an ultrasonic welding device of the present inventioneliminates the problem of the prior art i.e., when the side superimposedportion of the blank is welded with a conventional ultrasonic weldingdevice including a horn with a flat contacting surface, the adhesiongradually weakens from the center toward the outside of the horncontacting part, so that the ends of the sealed portion are not welded,cracks are formed at the central portion, and cracks are also formedwhen the sides of the blank is shifted in pressing the horn foroscillation.

Describing the second embodiment of the welding device of the presentinvention, as shown in FIGS. 8 and 9, an ultrasonic horn (H₂) has ashape such that a stepped portion 9 is formed at one edge of thecontacting surface of the horn to the side superimposed portion, andthis stepped portion is absent at the part corresponding to the vicinityof the upper end of the superimposed part. Describing the manner inwhich the ultrasonic horn (H₂) acts on the body superimposed part of thecontainer body, FIG. 11 shows the relative positions of the bodysuperimposed part and the horn seal wherein symbol A designates a blank,B is a sealed portion and C is the horn contacting position. When sealedby ultrasonic waves in this manner, the container is as shown in FIG. 4wherein the hatched part is the completely sealed part, and the part 3of the side seal 2 to 3 mm from the upper end is sealed widely so thatthe part most susceptible to cracks may be reinforced. FIG. 2 is asectional view along the line 2--2' of FIG. 3, and FIG. 4 is a sectionalview along the line 4--4' thereof. Referring to FIG. 4, the widelysealed portion 3 is a portion sealed by the non-stepped portion 8 of thehorn, and the completely adhered portion a and the non-sealed portion bare coexistant at the part of the sealed part below this portion 8.Symbol a denotes a sealed portion sealed by a lower surface 10 of thehorn, and the non-sealed portion b is the portion formed by the steppedportion 9 of the horn.

Finally, describing the method and device for forming the bottom part ofthe container of the present invention, numeral 17 denotes a mandrel and15 denotes an outer press mold in FIGS. 12, 13 and 14. The lower end ofa cup A is heat-sealed to the folded portion of a bottom plate B and Cis the adhering portion. Numeral 12 denotes a knurling tool, and 16 is acircular hole formed at the center of the outer press mold and having adiameter sufficiently greater than that of a knurling tool shaft 11. Theknurling tool is a disk which is smaller than the bottom adheringportion. The knurling tool rotates on its axis as well as along theinner wall of the circular hole at the center of the outer press mold.The adhering portion is strongly pressed between the mandrel 17 and theouter press mold 15. The outer circumferential wall 18 of the knurlingtool 12 has a tapered portion 13 like the tapered portion of a containersuch as a cup as shown in FIG. 13. Since an annular groove 14 of acertain width is formed at its central portion, the pressing forceagainst the adhering portion is great. Since the adhering portion has noprojections or recesses in the axial direction and is smooth, the bottompart is not of a zigzag form as in the conventional cases. Thus, nocracks are formed, no leakage of the contents is caused, and the outerappearance is superior.

Although the description has been made with respect to a containerhaving a frustoconical body, the same effects may be obtained with adisk-shaped knurling tool having a vertical outer circumferential wallfor a container having a cylindrical body.

What is claimed is:
 1. A container comprising a tubular frustoconicalside wall member having open ends, one of which is of smaller diameterthan the other and a flat circular bottom member disposed at the openend of smaller diameter; said side wall member comprising a trapezoidalblank laminate of two coextensive plies, one ply comprising cardboardand the other ply comprising plastic, said trapezoidal blank havingspaced, parallel top and bottom edges and symmetrically converging sideedges and said blank being formed to assume said tubular frustoconicalconfiguration with the cardboard ply at the outside and the plastic plyat the inside and with the side edges overlapping such that the plasticply at the inner marginal edge of the outer one of the side edges isdisposed in contact with the paperboard ply at the outer marginal edgeof the inner one of the side edges, said side wall member having at itsupper end a radially-disposed lip and at its lower end aninwardly-disposed upturned flange defining a groove peripherally of thelower end, the inner surface of which is constituted by the plastic plyand said bottom member corresponding in diameter to the open end ofsmaller diameter and being provided with a downturned peripheral flangeturned downwardly from the plastic side such as to have contact with theinner plastic side of the side wall member at the lower end and whereinthe cardboard ply at the marginal edge of the inner one of the sideedges is skived and the plastic ply at said marginal edge folded todispose the plastic ply about the end edge into contact with the plasticply at the inner side of the outer one of the side edges and wherein thelapped ends are ultrasonically bonded using an ultrasonic hornthroughout an area coextensive with the confronting overlapping surfacesthereof from the rim at the top downwardly along the overlappingsurfaces at least several millimeters to reinforce the top and whereinthe confronting overlapping surfaces of the lapped ends along theremainder of the distance toward the bottom are adhered to each otherthroughout an area corresponding in length to the remainder of thedistance toward the bottom and in width from the edge of the outer oneof the lapping ends toward the edge of the inner one of the lapping endsa distance less than the width of the overlapping surface such that theremainder of the confronting surfaces are unattached.
 2. A containeraccording to claim 1 wherein the plastic is polyethylene.
 3. A containeraccording to claim 1 wherein the sealed area at the top of the containeris 2 to 3 millimeters in length longitudinally of the side seam.